In the course of operation of a high-speed powerful turbogenerator, an appreciable field current is supplied to the rotor winding from contact brushes of the contact brush device through a slip ring supported on the rotor shaft and subjected to significant mechanical loads associated with a substantial rotational speed of the rotor shaft, which loads require the slip ring to be formed of high-strength metal. In this case, however, the high field current is discharged not from the whole ring but only from a portion thereof, due to certain structural considerations, thus giving rise to a temperature difference across the ring and hence resulting in rapid wear of the ring and brushes and deteriorating the field current transfer to the rotor winding, the adverse effect being aggravated by the low electrical characteristics of the ring material.
The present invention is directed to minimizing said temperature difference and, hence, improving the field current transfer.